An elevator installation comprises movable mechanical components such as a drive, cage and shaft doors, cage door drive, a cage door closing mechanism and guide rollers or guide shoes. Individual components are serviced at regular intervals in time and kept serviceable. The cost for such maintenance operations can be relatively inefficient, since the maintenance intervals are sometimes fixedly preset and are not necessarily oriented to the effective utilization of an actual elevator installation and the components thereof.
A possible indicator for the degree of wear of a moving mechanical component is represented by the degree of vibrations. In normal permissible operation a certain degree of vibrations is not exceeded. With progressive wear of a component the vibrations sometimes noticeably increase. If a predeterminable degree of vibrations is exceeded, then the point in time has been reached to restore the component to serviceability or to exchange it.
Vibrations propagate as sonic or solid-borne sound waves and are detectable by means of a sensor. As sonic waves there are to be understood here waves which propagate in a gaseous medium such as air and by solid-borne sound waves there are to be understood here waves which propagate in a solid medium such as steel or iron. Sensors designed as microphones, acceleration pick-ups or voltage measuring sensors are suitable for detection of sonic waves and solid-borne sound waves. An evaluating circuit is connected with one or more sensors. The evaluating circuit and at least one associated sensor form a monitoring unit. The evaluating circuit comprises a processor by which the evaluating circuit evaluates the detected sonic waves or solid-borne sound waves. The detected sonic waves or solid-borne sound waves can be evaluated in the evaluating circuit with respect to the amplitude and frequency thereof and compared with a predetermined value. Conclusions about the functional integrity of the elevator installation and its components can be made therefrom. In the case of exceeding a specific threshold value, a change-of-state alarm can be triggered.